1. Field of the Invention
The present invention relates to a device for controlling the rolling of four-wheeled vehicles, and more particularly, to such a roll control device for four-wheeled vehicles that controls the rolling without disturbing the turning course thereof.
2. Description of the Prior Art
The rolling of a vehicle body of a four-wheeled vehicle during its turn running can be suppressed by decelerating the vehicle or increasing the radius of curvature of the turning course, i.e. drifting out the vehicle, or doing both of these, because the lateral centrifugal force acting at the vehicle body which causes its rolling is proportional to the ratio of the square of the running speed of the vehicle to the radius of curvature of the turning course. Therefore, various roll control devices ever proposed are based upon the principle of decelerating the vehicle or drifting out the vehicle or doing both. A deceleration of a vehicle is of course available by actuating its brake system, while a drifting out of a vehicle is available by selectively actuating such a brake system that is adapted to be able to apply a controlled braking force to each one of the wheels independently of the other.
However, as well known in the art, a braking applied to a wheel necessarily causes a change the slip of the wheel against the road surface, particularly when the vehicle is running along a curved course so critically as to require a roll suppress control. Therefore, there is a problem that the braking for a roll suppress control induces instabilities of the course of driving, including an unintended increase of the radius of curvature of the turning course.